The present invention relates to the field of vane type compressors for compressing a gas such as a coolant gas, and in particular relates to an improvement in such vane type compressor which utilizes an improved material for the vanes thereof.
A vane type compressor generally comprises a cylinder block which is formed with a cylindrical bore, typically circular or elliptical, and end walls closing off this cylinder bore. A cylindrical rotor is received in the cylinder bore, with its axis parallel to or coincident with the axis of the bore, and a plurality of vanes are fitted into longitudinal slots formed in a generally radial direction in this rotor. As the rotor is rotated, a plurality of chambers are defined by these vanes as their outer edges slide against the wall of the bore, being biased thereagainst by the action of centrifugal force and possibly by the pressure of lubricant. As these chambers rotate around the cylinder bore, they expand and contract according to the particular configuration of the rotor and the bore, and by the provision of appropriate valving means these chambers are caused to perform compression and pumping of working fluid.
Conventionally, a type of material that has been utilized for these vanes has been cast high silicon aluminum alloy, which is light and wear resistant. However, this type of vane in some circumstances has a tendency to wear out rapidly, due to lack of lubricant when the lubricant layer on the tip edge portion of the vane fails as this tip edge slides over the surface of the cylinder bore, or when the lubricant layer between the side surfaces of the vane and the side surfaces of its slot in the rotor fails. This type of lubricant layer failure can particularly occur in the low speed high load operational condition.
Accordingly, in Japanese Patent Publication Ser. No. Sho. 58-77192, which it is not hereby intended to admit as prior art except to the extent otherwise prescribed by law, it was proposed to make the vanes for such a compressor from a material which was manufactured by impregnating a carbon preform with low melting point metal, such as aluminum or aluminum alloy, so that the self lubricating property of carbon should be combined with the strength of metal. However, this material is not completely satisfactory, because the bond between the carbon and the impregnating metal is typically not sufficiently strong, and accordingly the wear resistance of the vane is not found to be adequate, particularly since the vane is subjected to both heat and stress as it compresses the working fluid. Thus, prior art vane type compressors have left much to be desired with regard to the performance of the vanes thereof.